Net Income Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic
Net income applicable to common stock	$ 6,637	$ 7,037	$ 22,227	$ 19,356
Average common shares outstanding (shares)	27,234,927	25,114,672	25,889,139	25,101,507
Net income per common share - basic (usd per share)	$ 0.24	$ 0.28	$ 0.86	$ 0.77
Diluted
Net income applicable to common stock	$ 6,637	$ 7,037	$ 22,227	$ 19,356
Average common shares outstanding (shares)	27,234,927	25,114,672	25,889,139	25,101,507
Effect of dilutive stock-based compensation (shares)	212,455	106,215	164,034	60,404
Average common shares outstanding - diluted	27,447,382	25,220,887	26,053,173	25,161,911
Net income per common share - diluted (usd per share)	$ 0.24	$ 0.28	$ 0.85	$ 0.77